I have an older craftsman 42" riding mower.\r\nI replaced the madrel, pulley and belt.
All seemed good. Pulleys alined nice.
The new belt lasted 30 minutes and shreaded. Put the old belt back on and it lasted 15 minutes.
I read somewhere of spacers for the mandrelto save the belts. Any ideas?

Hi,
Sounds like you are getting it on the wrong side of a guide. All guides should be outside(touch the backside of the belt, if anywhere.)
Peace,
Clarke